Epidemic dengue fever (DF) and dengue hemorrhagic fever (DHF/DSS) have emerged throughout the tropical world with devastating public health consequences. A dramatic increase in severe dengue disease (DEN) in Latin America in the last decade is of grave concern; 30% of cases are now diagnosed as severe dengue virus (DENV) infections. DEN is overwhelming public health capacity for clinical care in much of the developing world. The overall goal of this proposal is to provide a major change in the diagnosis and prognosis (D&P) of DENV infections. A metabolomics approach will be used to identify candidate metabolite small molecule biomarkers (SMBs) that occur both in serum and in non-invasive clinical specimens (urine and saliva) that diagnose DENV infection and predict progression to severe disease. Preliminary studies using acute phase specimens from DEN patients have identified a number of molecular features and candidate SMBs of DF and DHF/SS in serum, saliva, and urine using liquid chromatography-mass spectrometry (LC-MS)-based metabolomics. In the R21 phase of this project, we will use a metabolic fingerprinting approach to confim existing and identify new candidate SMBs in retrospectively collected serum specimens available from the high-quality pediatric DEN hospital-based and cohort studies in Nicaragua, will begin to characterize the SMBs and metabolic pathways involved, will investigate the efficacy for D&P of these SMBs in prospectively collected serum, saliva, and urine specimens in the hospital study, and will identify a portfolio of the most significant molecular features that differentiate DEN, severe DEN, and non-DEN disease. We will develop algorithms including SMBs, clinical signs and symptoms, and clinical laboratory results for the D&P of DENV infections. In the R33 phase of the project, prospectively collected serum, saliva, and urine samples from both the hospital study and a community-based cohort study will be analyzed by metabolic profiling using LC-tandem MS (LC- MS/MS) to identify candidate SMBs. First generation EIA tests for selected SMBs will be included in the diagnostic regimen in Nicaragua The diagnostic and prognostic sensitivity and specificity of the candidate SMBs and first generation SMB tests will be determined as will the preferred clinical specimen for SMB- based diagnoses. Overall these studies will identify a panel of SMBs (e.g., 5-10), which will be used to formulate the Target Product Profiles (TPP) for rapid point-of-care (POC) tests for use in clinics and hospitals for DEN D&P. Detection of SMBs in saliva and urine that are predictive of severe DEN is innovative and provides the opportunity for a true paradigm shift in diagnosis by using inexpensive, easily procured, non- invasive clinical specimens for D&P of DEN.